In the art, for example from document EP 1 319 889 A1, it is known to energize a light-emitting diode inductively by using a primary coil and a secondary coil connected with the LEDs.
Generally, wireless powering and/or charging systems are frequently used in many applications. They allow powering of devices or charging of batteries (or capacitors) without electrical contacts. This is especially advantageous in environments where no electrical plugs and connectors are allowed, such as bathrooms and special rooms in hospitals, or where electrical plugs and connectors are not practical.
A wireless powering system is realized with the help of inductive coupling. Its power can be drawn from e.g. a public grid or from a battery. It is preferably realized as a resonant half-bridge or full-bridge converter with soft-switching behavior. A transformer enables the inductive coupling. The current through the primary coil of the transformer generates an alternating magnetic field. This alternating magnetic field generates a voltage in the secondary coil. The rectified voltage is then directly fed to a light source, like a light-emitting diode. Beside the aforementioned light-emitting diodes, so-called organic light-emitting diodes (OLED) are of growing interest and it is assumed that OLEDs will be a high potential future light source. This is due to their high efficiency and the cost-effective manufacturing. One of the most important advantages of OLEDs is their form factor, since they are thin and flat.
In many applications where LEDs or OLEDs can be used, the LED or OLED tiles have to be freely placeable and scaleable. Examples of such applications are general lighting systems, design lamps and decorative lights.
As a problem, devices with LEDs or OLEDs need to be powered or their batteries need to be recharged. In many environments, a conventional solution with electric contacts is subjected to pollution or to humidity. Additionally, open electric contacts cause short-circuit risks or shock danger. Thus, a wireless inductive charging method is preferred. In case of OLEDs the form factor (thin and flat) is important to designers and architects. However, standard drivers are bulky.